Hybrid Cu-Containing Compounds Based on Lacunary Strandberg Anions: Synthesis under Mild Conditions, Crystal Structure, and Magnetic Properties

Abstract

A one-pot reaction of a copper source (metallic powder Cu 0 or Cu 2+ salts) and bpy (bpy = 2,2′-bipyridine) in the presence of (NH 4 ) 2 HPO 4 and (NH 4 ) 6 Mo 7 O 24 •4H 2 O yields heterometallic hybrid compounds of the general type {[Cu-(bpy) n (H 2 O) m ] p [P 2 Mo x O y ]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P 2 Mo 5 O 23 ] 6− but also its unprecedented biand trilacunary derivatives [P 2 Mo 3 O 18 ] 8− and [P 2 Mo 2 O 15 ] 8− . The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different Cu II complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1−3 indicate rather strong antiferromagnetic metal−metal exchange interactions. Compound 1 exhibits fieldinduced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.

Slow magnetic relaxation of a S = 1/2 copper(ii)-substituted Keggin-type silicotungstate

“…The α parameter, which represents the dispersion of relaxation time, was quite small (0.04 < α < 0.11; for α = 0, single relaxation), which is characteristic of a highly isolated magnetic ion with a polyoxometalate skeleton. 4 a ,15–18 It should also be noted here that the obtained relaxation time ( τ = 92 ms at 1.8 K and H dc = 5000 Oe) is the longest among hitherto reported polyoxometalate-based transition-metal systems 17,18 and comparable to other potential room-temperature molecular spin qubits. 2,8…”

“…The α parameter, which represents the dispersion of relaxation time, was quite small (0.04 < α < 0.11; for α = 0, single relaxation), which is characteristic of a highly isolated magnetic ion with a polyoxometalate skeleton. 4a,15-18 It should also be noted here that the obtained relaxation time (τ = 92 ms at 1.8 K and H dc = 5000 Oe) is the longest among hitherto reported polyoxometalatebased transition-metal systems 17,18 and comparable to other potential room-temperature molecular spin qubits. 2,8 Relaxation time analysis An analysis of how the relaxation time varies with the static field and temperature was performed using direct and Raman spin-lattice processes as well as an inter-/intramolecular quantum-mechanical process (eqn (1)).…”

“…17 In addition, slow magnetic relaxation of the three S = 1/2-copper( ii )-containing Strandberg polyoxometalates has recently been reported. 18 However, to the best of our knowledge, the S = 1/2 systems of polyoxometalates with a single S = 1/2 magnetic center have not yet been reported. In this study, we investigated the spin-lattice relaxation of the tetrabutylammonium salt of an S = 1/2 copper( ii ) ion incorporated into an α-Keggin-type silicotungstate (Fig.…”

Constructing Two Cu-Modified Organophosphomolybdates from a Nanocluster to a One-Dimensional Chain for Boosted Visible-Light-Driven Hydrogen Production

“…In previous studies, most researchers selected Na 2 MoO 4 ·2H 2 O and (NH 4 ) 6 Mo 7 O 24 ·4H 2 O as inorganic precursors for obtaining {P 2 Mo 5 } unit. ,,, Here, we utilize MoO 3 and C 6 H 5 PO 3 H 2 to synthesize the {(C 6 H 5 P) 2 Mo 5 } unit by self-assembly. Compound 1 was prepared at 100 °C for 3 days, and crystals appeared in a wide pH range (pH = 2.5–4.5).…”

“…Yang’s group reported an Anderson–Evans polyoxometalate [Ni­(H 2 O) 6 ]­KH­[NiMo 6 O 24 (Sb 3 O 3 ) 2 ]·5H 2 O . The photocatalytic hydrogen production rate reached 10 358 μmol g –1 h –1 for 6 h. As for Strandberg-type POM, due to its relatively small size, it is easy to coordinate with metals to form stable clusters and is widely used in proton conduction, magnetism, electrochemistry, nonlinear optical materials, and other aspects of research. ,,, The application of photocatalytic hydrogen production has not been explored. Therefore, the rational design of Strandberg-type catalysts and the diligent exploration of visible-light-driven hydrogen production remains a significant challenge.…”